\textit{In situ} synchrotron radiation x-ray diffraction studies were performed on a
glass-ceramic nanocomposite on compression up to 43 GPa and on successive
decompression. The optically transparent material contained nanometer-sized
single crystalline phase homogeneously dispersed within an isotropic host
matrix. The pressure-evolution of x-ray diffraction patterns was consistent
with a phase transition occurring in the gallium oxide nanocrystals leading
to a metastable phase. This work is the first report of a pressure-induced
phase transition arising in the nanocrystalline phase of a glass-ceramic
composite that involves transition form a thermodynamically stable to an
unstable phase, maintained after pressure release, by the densified host
glass matrix.

*Supported by the DOE cooperative agreement FC08-01NW14049 and by DOE-NNSA (CDAC); HPCAT (Carnegie Institution, Lawrence Livermore National Laboratory, University of Hawaii, University of Nevada Las Vegas, Carnegie/DOE Alliance Center)

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.MAR.R1.216